The present invention relates generally to an automotive vehicle with an adjustable aerodynamic accessory which provides both an improvement in fuel economy and an improvement in driving stability. More particularly, the invention relates to a vehicle driving condition dependent control for the adjustable aerodynamic accessory of the automotive vehicle.
As is well known, the aerodynamics of an automotive vehicle are dominated by a drag coefficient Cd and a lift coefficient C.sub.L. In order to ensure high driving stability, the lift coefficient must be held to a minimum value. When the lift coefficient is a negative value, a downward force is applied to the vehicle body, providing enhanced road/tyre traction and so improving high-speed stability of the vehicle. On the other hand, the drag coefficient degrades fuel economy as its value increases. Furthermore, when only fuel economy is concerned, negative lift on the vehicle body for good road/tyre traction also has an adverse effect.
In order to improve vehicular aerodynamics, spoilers, such as a front or chin spoiler, a rear spoiler and so forth, have been used widely minimize the lift coefficient. However, such spoilers tend to increase the drag coefficient and so adversely affect fuel economy. Furthermore, front spoilers tend to increase the forward extent of the vehicle and so degrade fuel economy.
In consideration of the balance between driving stability and fuel economy, driving stability is more important than fuel economy when the vehicle is travelling at relatively high speeds, and on the other hand, fuel economy is more important than driving stability when the vehicle is travelling at relatively low speed.
Various aerodynamic accessory and controls have been proposed to provide a good balance between driving stability and fuel economy. For example, the Japanese Patent First Publications (Tokkai) Showa 54-131220, published Oct. 12, 1979, and Showa 58-22767, published on Feb. 10, 1983 disclose adjustable front spoilers which are movable between an extended position projecting from the lower edge of the front apron or air-dam of the vehicle body and a contracted position hidden behind the front apron, depending upon the vehicle driving speed. The Japanese Patent First Publication (Tokkai) Showa 58-22768, Feb. 10, 1983, discloses a front spoiler which can be operated in the contracted position in response to application of vehicular brakes. The Japanese Patent First Publication (Tokkai) Showa 58-85764, published on May 23, 1983, discloses an adjustable spoiler movable between extended and contracted positions depending upon air flow pressure at the front air-dam. The Japanese Patent First Publication No. 58-191672, published on Nov. 8, 1983 discloses a vehicle speed and vehicle height dependent front spoiler control.
However, the conventional spoiler control techniques are not considered to be complete since spoiler position can not be controlled precisely with regard to vehicle driving conditions.